1. Field of Invention
This invention relates to an apparatus for the ultrasonic welding of wires.
The apparatus includes a tip and associated means allowing for adjustment to accommodate different diameters of wire to be welded while maintaining a tight grip around the wires during the welding process to avoid spreading or splaying of the wires during the welding process. Further, the tip is rotatable to provide several alternative and interchangeable work surfaces on a standard-shaped readily machineable cross section, thereby allowing for a longer total worklife and a reduced cost of manufacture.
2. Description of the Prior Art
Wires may be ultrasonically welded to one another by placing the ends of the wires 7 firmly overlapping each other in a closed channel 1 formed between an ultrasonic welding tip 3 and a stationary support anvil 5 (as shown, e.g., in FIG. 1) and applying ultrasonic energy to the tip. The energy should be applied so that the tip vibrates parallel to the longitudinal axis of the wires to be welded, to intermolecularly bond the wire ends.
In order to assure that the vibrational energy is efficiently transmitted to the wires or workpiece, both the tip and the anvil have a serrated worksurface 9 for holding the wires or workpiece firmly in place.
Methods of generation of ultrasonic vibration are wellknown in the prior art (e.g., U.S. Pat. Nos. 3,053,124; 3,328,610; 3,444,612; and 3,602,421). A typical frequency of vibration may be twenty thousand cycles per second.
In order to prevent spreading or splaying of the wire or workpiece during the welding process, the wire or workpiece should be tightly confined within a compression chamber. Further, any change in the number or size of these wires or workpieces requires adjustment of the cross-sectional area of this chamber. It is desirable that this adjustment be done without the replacement of apparatus. Additionally, it is desirable that multiple available worksurfaces be provided in order to quickly replace any exhausted worksurfaces. This should be accomplished with easily machineable simply-shaped apparatus.
Along these lines, the device as shown in FIG. 1 has a number of disadvantages. First, the wires to be welded are held in a channel formed by the intersection of a notch 4 on the tip 3 and a notch 2 on the anvil 5. As the size of the mating notches 2,4 is not adjustable and the tolerance between the tip 3 and the anvil 5 along with the firmness of the serrated worksurface 9 on the workpiece or wires 7 is critical in order to prevent the wire end from extruding or splaying while in a plastic state during the welding process, a given tip is generally applicable to the welding of only one size of wire, or a limited number of ends thereof. A machine shop having occasion to weld various sizes of wires would have to obtain ultrasonic welding tips of corresponding notch sizes.
Secondly, the tip and the anvil have intricate shapes and the notches therein must be manufactured within close tolerances, thereby adding to manufacturing costs.
Lastly, the welding tip 3, as shown in FIG. 1, presents only two possible work surfaces 9. After the first worksurfaces 9 is exhausted, in that the gripping serrations and dimensional tolerances become worn after repeated use, the tip is rotated 180.degree. to present a second serrated, gripping worksurface. After this second worksurface is exhausted, the tip is discarded.
As previously described, the manufacturing costs of this tip are high and a supply of tips with varying sizes of notches must be kept by the well-supplied machine shop; therefore, the frequent discarding of these tips may present both a financial and a procurement concern.